: Since blue can mean profane, the stream of words could be one epithet after another. This would result in "cursing a blue streak".

As "Blue Streak" was an expensive bomber-delivered (nuclear?) missile programme in the 50s-60s - to have one fall either on one's home or foot would be a catastrophe, as would paying for one out of one's pay if one went astray during a routine stock-audit. It would be no surprise if somebody then cursed a blue streak.